I can only assume 91+ octane fuel aswell or atleast hope you are using it.

Plugs are too cold for those mods, some AL 605's would be a better choice.

And what gap are the plugs at?? I'd lower them to .050 if they are larger.

Clean all coil pack terminals and use some electronic grease on them aswell, do all the little things to see if any of them do a fix.